Method of fabricating cellular foam core structure assembly

ABSTRACT

A series of preformed, elongated foam cores are positioned generally longitudinally parallel and transversely aligned and are covered with primary base and covering layers of a relatively flexible fabric, such as fiber glass. In the assembly, the primary base layer extends continuously along common lower base sides of the foam cores, while the primary covering layer extends continuously upwardly over and downwardly transversely between the foam cores, the primary layers being stitched at the transverse extremities of each of the foam cores. Depending on the transverse cross sectional configurations of the foam cores, the stitched primary layer and core assemblies may be used separately or with one inverted and assembled interfitting with another, and may be shaped in various configurations and sandwiched between continuous secondary covering layers of fabric, in all cases all of the fabric layers and stitching being completely covered and impregnated with resin cured to rigidify the overall assembly. Still further, such assemblies may be incorporated with the rigid, thickened face layer of various materials and configurations at one or both sides thereof, for instance, a thickened face layer of cured resin.

United States Patent Corzine [151 3,658,612 [451 Apr. 25, 1972 [54]METHOD OF FABRICATING CELLULAR FOAM CORE STRUCTURE ASSEMBLY [72]Inventor: Luke 11. Corzine, Lakewood, Calif.

[73] Assignee: Unicor1nc., Paramount, Calif.

['22] Filed: Oct. 24, 1969 [21] App]. No.: 869,073

Related US. Application Data [60] Division of Ser. No. 819,796, Apr. 28,1969, which is a continuation-in-part of Ser, No. 383,390, July 17,

1964, abandoned.

[52] U.S.Cl ..156/93,161/135, 161/36 [51] Int. Cl ..B32b 7/08 [58] Fieldof Search ..l61/36, 135, 309; 156/93, 91; 52/309 56] References CitedUNITED STATES PATENTS 2,692,219 10/1954 Slayter et a1. ..l56/93 X2,737,227 3/1956 Brummel ....156/93 X 2,788,053 4/1957 Dolbey et al.......156/93 X 2,948,950 8/1960 Finger et al. ..161/135 X 3,117,902 1/1964Holzheimer..... ....161/36 X 3,145,131 8/1964 Finke ..161/36 3,188,8136/1965 Foster et al. ..l61/135 Beckman et al. ..16l/135 X Derr et al..52/309 [57] ABSTRACT A series of preformed, elongated foam cores arepositioned generally longitudinally parallel and transversely alignedand are covered with primary base and covering layers of a relativelyflexible fabric, such as fiber glass. in the assembly, the primary baselayer extends continuously along common lower base sides of the foamcores, while the primary covering layer extends continuously upwardlyover and downwardly transversely between the foam cores, the primarylayers being stitched at the transverse extremities of each of the foamcores. Depending on the transverse cross sectional configurations of thefoam cores, the stitched primary layer and core assemblies may be usedseparately or with one inverted and assembled interfitting with another,and may be shaped in various configurations and sandwiched betweencontinuous secondary covering layers of fabric, in all cases all of thefabric layers and stitching being completely covered and impregnatedwith resin cured to rigidify the overall assembly. Still further, suchassemblies may be incorporated with the rigid, thickened face layer ofvarious materials and configurations at one or both sides thereof, forinstance, a thickened face layer of cured resin.

10 Claims, 14 Drawing Figures Pal :ented April 25, 1972 r 3,658;612

3 Sheets-Sheet l mum/70R LUKE hi CaQZ/NE Patented April 25, 1972 3Sheets-Sheet z .Fi'ra. 6.

lA/VEA/TOR uKE hf CORZ/NE Patented A ril 25, 1972 3,658,612

3 Sheets-Sheet 3 wvzu r02 LUKE H. CORZ/NE METHOD OF FABRICATING CELLULARFOAM CORE STRUCTURE ASSEMBLY CROSS-REFERENCE TO RELATED APPLICATIONSThis application is a division of my co-pending application Ser. No.819,796, filed Apr. 28, 1969, entitled, Cellular I Foam Core StructureAssembly and Method of Fabrication,"

BACKGROUND OF THE INVENTION This invention relates to methods-offabricating cellular foam core structure assemblies, and moreparticularly to such methods which are adaptable in a relatively simplemanner to an extremely wide variety of uses. For instance, using thesame basic procedures and with a proper selection of foam coreconfiguration, the basic cellular foam core structure assembly may beintegrated into wood, composition or-metal based panel structures havinga wide variety of plane or curved shapes, and is equally adaptable tovarious plastic constructions. Furthermore, the basic cellular foam corestructure assembly includes a series of preformed foam cores of a closedcell plastic foam material which are covered in a particular assembledposition by specifically shaped primary base and covering layers of aflexible fabric material and the fabric material layers stitched betweenfoam cores for retaining such assembly. In final overall assembly, asselectively integrated with various face coatings and secondary coveringfabric layers, the basic assembly has all of the fabric layers andstitching covered and impregnated with a resin which is cured after saidcovering and impregnation to provide a final basic assembly havingrelatively high structural strength in the overall assembly despite thesimplicity of construction and the wide versatility of use.

Many forms of composite cellular foam and resin rigidified fabricstructures have heretofore been provided, all of which have seriousinherent limitations and most of which may'only be applied to particularcustomized uses. One of the more prevalent of theseprior constructionsis the honeycomb core structure or similar, slightly changedadaptations-thereof. In the honeycomb core or similar structures, thebasic core consists of a mass of adjacent compartments formed by edgepositioned fabric strips covered, sometimesimpregnated, and

rigidified by a cured resin, the thusly formed compartments later beingfilled by a cellular foam to complete the basic core assembly and thencovered by sheets of resin rigidified fabrics and other structuralmaterials for the overall assembly. I

In the specific procedures of forming these prior honeycomb and similarbasic core structures, the most common method is to first form thefabric strips while the fabric is in a flexible condition into thehoneycomb or other adjacent compartment configurations, while at thesame time, conforming this then flexible fabric into the desired shapeof the final overall assembly. The fabric strips are then resin coated,sometimes resin impregnated, and cured to place the specificallyconfigured fabric strips in a rigidified and form retaining condition.The final basic core structure is then completed by foam filling therigidly retained compartments with a cellular foam which is normallychemically cured during and immediately following such installation.

Under certain relatively limited conditions, it has been possible tooriginally form the edge positioned fabric strips into the honeycomb andsimilarly shaped compartment form and cured resin rigidify the samewhile the fabric edges are resting on a plane surface resulting in acompartmentalized shell defining such plane surface. In this case, theresin rigidified shell may be formed into limited curved configurationswherein the compartment openings and the rigidified fabric edges definesomewhat curved surfaces as desired in the final overall assembly. Theextent to which this originally rigidified flat shell may be shaped intothe curved surface defining formation is, of: course, determined'by theinherent combinedflexibility of the fabric and cured resin, but inanyevent, it is only after this curved-surface formation that the finalfoam filling may take place in-orderto complete the-basic assembly.

Thus, despitetheparticular procedure followed-in the fabrication andformation' of these'prior honeycomb and similarly shaped basiccore'structuresthe. designed use thereof is always further limited andrestricted to an overallfmal structure that permits installation ofthefoam into-the compartments of the core'shell during'the final overallassembly. This requirement alone greatly restricts the designs'to whichsuch-prior core structures may be adapted. Also, exceptaspermittedbytheextremely small range of flexibility ofthe cured resin rigidified fabricin the latter fabrication procedure, these prior core structures alwaysrequire the formation of a specific custom structure usable only in anexactly predeterminedfinal' overall-structure so'thatmodular basic corestructure formation is virtually eliminated.

OBJECTS AND SUMMARY'OFTI-IE INVENTION It is, therefore, an object ofthis invention to provide methods of fabricating cellular foam corestructure assemblies wherein the basic cellular foamcore structure,later integrated into the final overall assembly, is adaptable to bothcustomized fabrication and usewhere particular conditions dictate, andfor widely versatile modular fabrication and use under many otherconditions. With the basic cellular foam structure of thepresent-invention, whether incustomized or modular form, there are nolimitations placed on the final overall assembly by the requirement ofaccessibility to-install the cellular foam, since the cellul'arfoamisoriginally placed in the basic structure in virtually its final formprior to any attempt to integrate the basic structure into the finaloverall assembly. Furthermore, there are'no limitations as tofabricflexibility in a resin'rigi'difiedform, nor any furtherlimitations on fabric weave or original formation, thefabric alwaysremaining in its original-flexible form-until-integration into and thefinal fabrication of the overall-assembly, despite the: fact that thebasic core structure is of a self integrated form at the rim ofinclusion into the'final overall assernbly.

It isa further object of this invention to provide methods offabricating cellular foam core structure assemblies having all of theforegoing advantageous attributes, yet'the basic core structure is of anextremely simple and easily fabricated form, and is integrated into thefinaloverall assembly with maximum ease andconvenience. In generalterms, the basic core structure consists of a series 'of preformed,elongated, cellular foam cores positionedgenerally parallelinlongitudinal extension and generally transversely aligned, said coresbeing of defined transverse cross sections depending on the intendedfinal structure use, whether of customized form or versatile modularform. A primaryv base layer of fabric underlies the thusly positionedfoam cores'and a primary covering layer of fabric extends continuouslyupwardly over each of the cores to and from the primary base layer, theprimary base and covering layers being stitchedtogether at thetransverse extremities of each of the cores completing a self-containedassembly wherein the fabric is still in its originally woven flexibleform.

At this stage, the basic core structure is ready for integration intothe overall assembly and with the fabric'still in itsoriginal flexibleform, the basic core structure may be freely shaped to conform to thedesired final overall assembly with only a modified limitation in suchshaping by virtue of the preformed foam cores. In thisrespect, however,the transverse crosssectional shapes of the preformed foam cores, whichmay be uniform throughout or differentat various locations, will to agreat extent determine the overall flexibility and the typeoffinal'assembly shaping to which the basic core'structure may besubjected transversely of the foam cores, and the inherent cellular foamcomposition of the foam cores will permit a limited amount of flexinglongitudinally thereof without destructive fracture and while stillmaintaining structural integrity. The basic core structure may beflexibly shaped and formed into the final overall assembly as a singleunit, or with particular foam core cross sectional shapes andpositioning, with a similar basic core structure in a sandwich assemblyas a unit, in either case the flexible fabric of the basic corestructure being coated and impregnated with a wet resin which is laterrigidified by curing .to rigidify and resin bond the final overallassembly. In addition, the final overall assembly may include resinrigidified secondary covering layers of fabric and thickened face coatsor layers of various materials, all integrated with the basic corestructure or structures preferably through cured resin bonding.

It is evidence, therefore, that the method of fabricating cellular foamcore structure assemblies of the present invention involves basicconcepts completely the reverse of the prior composite foam and resinrigidified fabric constructions hereinbefore discussed, such as thehoneycomb and similarly shaped basic core structures. In the priorstructures, the originally flexible fabric is formed into final shape,cured resin rigidified and then made use of to support the laterinstalled cellular foam, such required procedure creating seriouslimitations in use of such structures and requiring each to be ofcustomized form. According to the principles of the present invention,however, the cellular foam is originally preformed into determined crosssection cores of configurations which will not greatly inhibit butrather actually complement the flexibility of the basic core structures,and these preformed foam cores are used to support the flexible fabricduring the integration of the basic core structure into the finaloverall assembly with the same only being required to be cured resinrigidified in the final stages of integration into the overall assemblyso as to permit adaptation to a wide variety of final shapes.

Other objects and advantages of the invention will be apparent from thefollowing specification and the accompanying drawings which are for thepurpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, withparts broken away, illustrating two, substantially identical, basiccellular foam core structures, each in subassembly with asecondary'covering fabric layer, ready for further assembly into asandwich construction, all according to certain of the principles of thepresent invention;

FIG. 2 is an enlarged, fragmentary, vertical sectional view takentransversely of the foam cores and illustrating the foam core structuresubassemblies of FIG. 1 in their final sandwich construction includingcured resin rigidifying and resin bond- "'8;

FIGS. 3, 4 and 5 are views similar to FIG. 2, but illustrating differentforms of foam core structure subassemblies in various sandwichconstructions;

FIGS. 6, 7 and 8 are views similar to FIG. 2, but illustrating variousforms of basic foam core structures adapted for separate use and priorto any cured resin rigidifying or integration into any subassemblies orfinal overall assemblies;

FIG. 9 is a fragmentary, vertical sectional view of a final overallassembly incorporating a basic foam core structure or structures havingappropriately mixed transverse cross sectionally configured foam corestherein adapting the same for a particular final curvature;

FIGS. 10, ll, 12 and 13 are fragmentary, vertical sectional viewsillustrating the fabrication steps in the mold lay-up of the finaloverall assembly of FIG. 9; and

FIG. 14 is a fragmentary, vertical sectional view of a final overallassembly incorporating the basic foam core structure of FIG. 7. v

DESCRIPTION OF THE BEST EMBODIMENTS CONTEMPLATED As hereinbefore pointedout, the methods of the present invention involve the fabrication ofbasic cellular foam core structures which are relatively simple instructural form, yet having extremely wide versatility and adapted forintegration into a great variety of overall final assemblies. It is theintent in the drawings of the present application and in the followingdescription and discussion to illustrate and specifically describe thebasic cellular foam core structure elements, the fabrication of variousbasic cellular foam core structures having presently conceived uses, andcertain final overall assemblies with the procedural steps forfabricating the same integrating various of the basic cellular foam corestructures therein, all constituting parts of the present invention. Itis not intended, however, by such illustrations, descriptions anddiscussions to limit the broader principles of the present invention tothese particular embodiments, and it is envisioned that many future useswill be conceived, all within the scope of the present invention.

Referring to FIGS. 1 and 2 of the drawings, an embodiment of basiccellular foam core structure is shown adapted for integration into asandwich assembly and having certain uses in singular form. The sandwichconstruction is illustrated and makes use of two of the basic cellularfoam core structures, one inverted and inter-engaged downwardly fullywith the other. As is broadly true of all of the basic cellular foamcore structures of the present invention, the basic structure hereininvolved includes a series of preformed, elongated, cellular foam coresgenerally indicated at 20, a primary base layer of fabric 22, a primarycovering layer of fabric 24 and a series of specifically located linesof stitching 26.

Each of the cellular foam cores 20 is preformed prior to even assemblyinto the basic cellular foam core structure from a closed cell plasticfoam material such as polyurethane and similar plastic foam materials sothat each of the foam cores is of a shape self-sustaining constructionat the time of assembly into the basic core structure. In the formationof the basic core structure, a series of the foam cores 20 arepositioned substantially parallel in their longitudinal extension,substantially transversely aligned and in this case transverselyadjacent. Furthermore, each of the foam cores 20 is of the sameisosceles triangular shape in transverse cross section so as to have intransverse cross section substantially flat sides consisting of a lowerbase side 28 and generally oppositely transversely facing sides 30joined at the core upper extremity.

Continuing with the assembly of the basic core structure, the primarybase layer of fabric 22 is positioned extending continuouslylongitudinally and transversely along and between all of the foam corelower base sides 28 while being maintained substantially free of upwardprojection between the foam cores 20. The primary base layer of fabric22, as is true of all other fabric layers used in the basic corestructure and in most cases throughout cellular foam core structureassemblies, may be a single or multiple ply layer of virtually any weaveand of virtually any usual flexible fabric material, such as animal,vegetable and synthetic fibers with fiberglass fibers being preferredfor their strength and nondeteriorating qualities in a large number ofinstances, the choice of weave and fabric material being dependent onthe desired characteristics of the finished product. Also, in the basiccore structure, and until ready for integration into an overall or finalcellular foam core structure subassembly or assembly, the fabric makingup the primary base layer 22 remains in its flexible state.

The primary covering layer of fabric 24 of similar flexible fabric ispositioned extending continuously longitudinally-and transversely overand between the foam core oppositely transversely facing sides 30 so asto cover all of the foam cores 20 upwardly over the upper extremitiesand contact the primary base layer 22 transversely between the foamcores. The primary covering layer 24 again remains in its flexible stateand the basic core structure is completed by stitching transverselybetween each of the foam cores to secure the primary base and coveringlayers 22 and 24 together forming the lines of stitching 26, thestitching thread being any of the usual materials and preferably thesame as that making up the fabric of the primary base and coveringlayers. Thus, in the completed basic core structure, the flexibleprimary base and covering layers 22 and 24 abut all of the flat sides 28and 30 of all of the foam cores 20 so that the foam cores support theselayers at this stage and will continue to do so during integration intothe final subassemblies and assemblies, but at the same time, thesestitched flexible fabric layers provide complete transverse flexibilityof the structure within the limitations of the foam core transversecorss sections and reasonable longitudinal flexibility within thelimitations of the foam core internal closed cell constructions.

Although the basic core structure as fabricated with the isoscelestriangular configurations of the foam cores 20 has a variety of uses inboth singular and multiple form depending on the particular finalcellular foam core structure assembly into which it is integrated andthe purpose of such final assembly, in the illustration of FIGS. 1 and2, the basic core structures are integrated into a sandwich assemblywherein one is inverted and interengaged downwardly fully with another.In forming such assembly, the basic core structures have the primarybase and covering layers 22 and 24 thereof thoroughly coated andimpregnated with a curable wet resin which may be of usual forms such aspolyester, epoxy and phenolic resins, and which may be catalyzed toproduce rigidifying cures at room temperatures or elevated temperatures,again dependent on the particular characteristics desired, theparticular uses and the particular final assemblies. Furthermore, in theparticular final assembly of FIGS. 1 and 2, a secondary covering layerof fabric 32 is positioned in flexible state over and continuouslycovering the primary base layer 22 of each of the basic core structuresand is covered and im pregnated with the curable-wet resin, it beingnoted that the secondary covering layers likewise do not projectupwardly transversely between the foam cores 20, but rather remain onlyas covering layers.

Thereafter, the basic core structures with their assembled secondarycovering layers 32 are brought into final sandwich interengaged assemblyin the still flexible and wet state in the manner shown in FIG. 2. Thisfinal sandwich assembly is then retained in the final desired shapewhile the resin curing and rigidifying is carried out, the resinrigidifying causing rigidifying of the entire assembly and the resinbonding of abutting fabric layers in and between the basic corestructures, including the stitching 26 and the fabric layers at theseareas of the basic core structure. If the resin is catalyzed to producecuring at room temperature, the sandwich assembly is merely retained inthe final desired shape for a curing period of time, and if the resin iscatalyzed to produce curing at elevated temperatures, the sandwichassembly is raised to such elevated temperatures and retained for thecuring time, thereby producing a finally rigidified overall assembly.

As shown in FIG. 2, the sandwich assembly has been shaped for finalcuring and rigidifying so as to produce a final flat panel, and with theidentically sized and shaped foam cores 20, this will produce themaximum contact and resin bond between the parts of the primary coveringlayers 24 abutting transversely between the foam cores at the foam corefacing sides 30 resulting in a virtually solid integrated final overallassembly. While in the fully interengaged sandwich assembly of FIG. 2and with the basic core structures still in the resin wet stage, it ispossible to form limited curved shapes in either or both of thetransverse and longitudinal directions within the limits of the inherentflexibility of the closed cell compositions of the foam cores 20, butwithout actually fracturing or otherwise damaging the cellular structureof the foam cores. More sharp curved shaping, however, and particularlyin the assembly transverse direction, would require less interengagementbetween the individual basic core structures although this would stillin finally cured resin rigidified state produce a relatively strongfinal assembly, as long as some abutment is maintained between the partsof the primary covering layer at the foam core facing sides 30.

In other words, the versatility of even this sandwich form of assemblyin various curved forming is relatively great and a wide choice ispresented, depending on the ultimate strength,

shaping and structural integrity required. Also, this final sandwichassembly, as well as other assemblies and individual basic corestructures may be combined still further with various materials, eitherin thewet stage prior to resin. curing and rigidifying or after suchcuring and rigidifying. Certain of these more complex assemblies usingother basic core structures will be hereinafter described more indetail, but it should be kept in mind that the just-described sandwichassembly is equally adaptable.

A different final sandwich assembly using two basic core structures isshown in FIG. 3, wherein each of the basic core structures is againidentical, but of slightly different configu ration. As shown in FIG. 3,a series of elongated foam cores 34 are again positioned parallel inlongitudinal extension and generally transversely aligned, the foamcores again being triangular in transverse cross section, but crosssectionally defining right triangles positioned in transversely adjacentsets. Each of the foam cores 54 has a lower base side 36 and may begenerally described as having oppositely transversely facing sides, inthis case, an upright side 38 and an angled side 40, all sides againbeing flat. 7

Still referring to the individual basic core structures, the sets offoam cores 34 are positioned with the upright sides 38 adjacent so thatthe angled sides 40 of a given set generally transversely face theangled sides of the adjacent foam core-sets. A primary base layer offlexible fabric 42 is positioned extending along the foam core lowerbase sides 36 continuously longitudinally and transversely of the foamcores and between said cores, with a primary covering layer of flexiblefabric 44 extending continuously upwardly over the foam core upright andangled sides 36 and 40 including along the upright sides downwardlybetween the foam cores 34 of each set. The basic core structures arecompleted ready for integration into a final sandwich assembly bysecurement of the primary base and covering layers 42 and 44 in theircovering positions over the foam cores 34 by lines of stitching 46 atthe transverse extremities of each of the foam cores between the primarybase and covering layers as shown.

The final assembly of the basic foam cores into the sandwich assembly isvirtually the same as previously described, that is, the primary baseand covering layers 42 and 44 and the stitching 46 are covered andimpregnated with the curable wet resin, secondary covering layers 48 ofresin covered and impregnated fabric are applied to the primary baselayers, the basic core structures interengagingly assembled and theentire assembly cured to rigidify the resin. The same wide choice ofmaterials may be used in this assembly as in all other assemblies andstructures herein described, and the same wide choice of forming ispresented within the limits of the various materialsused.

Two still different final sandwich assemblies are shown in FIGS. 4 and5, formed in generally the same manner and from the same materials asthose of FIGS. 1 through 3, but involving a slightly different conceptof foam core positioning and sandwich interengagement to provide certainspecific final qualities. The .difference'in basic concept of the finalsandwich assemblies of FIGS. 4'and 5 is that not only are the foam coresthereof in the individual basic core structure formed with four or anadditional flat side, the-individual foam cores of each of the basiccore structures are transversely spaced uniformly apart. Thus, where thefinalsandwich assemblies are desired to be in the flat panel form, asshown, in the final, resin cured, rigidified state, increased overallfabric surface contact is obtained between the basic core structures forincreased cured resin bonding so as to increase atleast shearingstrength within the final assembly parallel to the final flat surfacesthereof.

Generally, as before, the sandwich assembly of FIG. 4 has the individualbasic core structures each formed with foam cores 50, a flexible fabricprimary base layer 52, a flexible fabric primary covering layer 54 andlines of stitching 56, the

' basic core structures ultimately receiving the flexible fabricsecondary covering layers 58 at the time of assembly. The foam cores 50are, however, rectangular in transverse cross section and spacedtransversely apart so that the lines of stitching 56 at the transverseextremities of the foam cores result in two lines of stitching betweeneach set of foam cores spaced transversely apart andrthe primary baseand covering layers 52. and 54 extending abutting transversely betweenthe foam cores, one to the next. In the final sandwich assembly,therefore, the parts of the primary covering layers 54 at upperflat-sides 60 give increased-surface abutment between the basic corestructures for increased shear strength parallel to the flat sides ofthe flnal sandwich assembly, and slightly less surface contact atupright, transversely opposed sides 62 of the foam cores.

The basic core structures of the sandwich assembly of FIG. also includefoam cores 64, flexible fabric primary base layers 66, flexible fabricprimary covering layers 68 and lines of stitching 70, with the lateradded flexible fabric secondary covering layers 72. Furthermore, thefoam cores 64 are in the transversely spaced positions with the doublestitching, but the foam cores are of isosceles trapezoidal transversecross sections with major base sides 74 at the primary base layer 66 andminor or shortened base sides 76 spaced away from the primary baselayer. Thus, in the finalsandwich assembly of FIG. 5, there is reducedsurface abutment between the parts of the primary covering layers 68 ofthe basic core structures at the foam core shortened base sides 76slightly reducing the shear strength thereof parallel to the sandwichassembly flat sides, while increased surface contact or abutment betweenthe foam cores at foam core transversely opposed sides 78, againillustrating the wide versatility and wide choice of strength featuresthat may be incorporated into the cellular foam core structuresand'assemblies of the present invention.

In FIGS. 6, 7 and 8 are shown examples of different basic corestructures according to the present invention which are normally usedsingularly, as opposed to the foregoing sandwich construction. Each ofthese basic core structures has particular versatility and those ofFIGS. 7 and i providing the most advantages for reasons to be hereinpointed out.

I The basic core structure of FIG. 6-is of quite limited use and it isbasically different from the other structures herein involved in that itincludes two primary covering layers 80 of flexible fabric continuouslycovering foam cores 82 of rectangular cross section and stitched bylines of stitching 84 midway of foam core transversely facingsides 86.The foam cores 82 may be transversely positioned spaced slightly apartto provide increased flexing formability or may have the parts of theprimary covering layers 80 at the transversely facing sides 86 thereofclosely abutting for less flexing and more solid resin rigidified finalform. It is apparent, however, that far less flexibility in formation isprovided with this construction, due to the midway covering layerstitching.

The more versatile basic core structure of FIG. 7 includes transverselyadjacent, rectangular transverse cross section foam cores 88, a flexiblefabric primary base layer 90, a flexible fabric primary covering layer92 and lines of stitching 94 between the primary base and coveringlayers along the transverse extremities of the foam cores. The primarybase layer 90 extends continuously along lower base sides 96 of the foamcores 88 without projecting upwardly transversely therebetweemwhile theprimary covering layer 92 extends continuously upwardly over upright,transversely opposed sides 98 and upper extremity sides 100 of the foamcores from and to the primary base layer and the lines of stitching 94between said layers. Obviously, the basic core structure of FIG. 7provides extreme flexibility in the transverse direction before curing,since the foam cores 88 may be spread angularly apart in any degreedesired prior to integration into a flnal overall assembly combined withother fabric layers and face surfaces or layers of various types,certain of which will be hereinafier illustrated and described. Thefinal resin rigidifying of the basic core structure is accomplished inthe same manner as previously described.

The basic core structure of FIG. 8 is even more versatile for curvedformation prior to resin rigidifying than that of FIG. 7

and includes foam cores 102, a flexible fabric primary base layer 104, aflexible fabric primary covering layer 106 and lines of stitching 108.The foam cores 102 are isosceles trapezoidal in transverse cross sectionpositioned with major base sides transversely adjacent and continuouslycovered by the primary base layer 104 and the primary covering layer 106extending continuously from and to the primary base layer alongtransversely opposed or facing sides 112 upwardly over upper extremityminor base sides 114. Thus, in flexible form prior to resin rigidifyingand in view of the primary base layer 104 not extending upwardlytransversely between the foam cores 102, the basic core structure ofFIG. 8 may be transversely flexed by flexing of the fabric layersbetween the foam cores in the one direction until the parts oftheprimary covering layer 106 over the foam core transversely facing sides112 abut, and in the other direction almost unlimited.

Still a further important versatility feature of the cellular foam corestructures and assemblies formed by the methods of the present inventionis that for custome overall assemblies, and even in certain cases ofsomewhat modular use, foam cores of different transverse cross sectionsmay be intermixed in a single basic core structure or in an assembly ofa series of basic core structures. For instance, in FIG. 9 isillustrated a final overall assembly making use of foam cores 116 ofmixed rectangular and isosceles trapezoidal transverse cross sections inorder to lay up a boat hull having compound curving while stillproviding a solid foam and resin rigidifled fabric hull construction.The basic core structures used are in the singular form such as those ofFIGS. 7 and 8 wherein the foam cores 116 are transversely adjacent andthe section of FIG. 9 is transversely through the basic core structureand the foam cores thereof.

The procedural or method steps for forming the boat hull of FIG. 9 areshown in FIGS. 10 through 13, and as would be the usual practice, thelay up is accomplished in a usual form of mold' 118. The materials usedin this case .are preferably preformed foam. cores 116 of closed cellpolyurethane foam, a flexible fabric primary base layer of fiberglass120, a flexible fabric primary covering layer of fiberglass 122, aflexible fabric secondary covering layer of fiberglass 124 covering theprimary base layer l20,a flexible fabric secondary covering layer offiberglass 126 covering the parts of the primary covering layer 122 at'the foam core upper extremities, and a thickened outer facing or layer128 of colored resin. The resin used for rigidifying after curing of thevarious fabric layers and that of the thickened outer facing 128 maybethe same and may be of any of the usual forms catalyzed for curingeither at room temperature or elevated temperatures, the latter beingpreferred.

Referring to FIG. 10. the thickened outer facing 128 of wet resin isapplied to the molding surface 130 of the mold 118, and although notshown for simplification purposes in FIGS. 10 and 13, it will be notedin FIG. 9 that the molding surface curves rather sharply transversely ofthe basic core structure, thereby illustrating compound curving. Next,the flexible fabric secondarycovering layer 126 is applied to the innersurface of the thickened outer facing 128 as shown in FIG. 11 and is wetresin covered and impregnated, this subassembly then being resin curedto rigidify the same. This subassembly is then ready for integrationwith the basic core structure.

Thebasic core structure is preassembled in flexible form in the mannerdescribed relative to those of FIGS. 7 and 8, except that the foam cores116 are of predetermined mixed transverse rectangular and isoscelestriangular cross section. As is evident, the isosceles triangular crosssection cores permit the relatively sharp transverse curving while stillresulting in a solid core assembly and the rectangular cross sectioncores are located at the flat or substantially flat portions of thehull.

The primary base and covering layers of the basic core structure,including the previously described lines of stitching thereof (notshown), are wet covered and impregnated with resin, as shown in FIG. 12,laid up against the previously resin cured subassembly of the secondarycovering layer 126 and the thickened outer facing 128. During suchlaying up, the primary base layer 120 of the basic core structure isretained at the outer side directly'against the rigidified secondarycovering layer 126 with the upper extremities of the foam cores 116 andthe parts of the primary covering layer 122 thereover projectinginwardly and, at this stage, still exposed. The still wet and flexiblebasic core structure will, therefore, be formed curved transversely tobring the foam core transverse sides and the parts of the primarycovering layer 122 thereover into transverse abutment as precalculatedby the preforming of the foam core transverse cross sections, while atthe same time, the foam cores 1 l6 and their fabric layers will begently flexed curved longitudinally of the basic core structure withinthe limits of the foam core closed cell constructions.

Finally, as shown in FIG. 13, the flexible fabric secondary coveringlayer 124 is applied covering the upper extremities of the foam cores116 and the parts of the primary covering layer 122 thereover, and aspositioned, this secondary covering layer 124 extends merelycontinuously along the basic core structure as formed and does notproject transversely between the adjacent foam cores 116. The secondarycovering layer 124 is covered and impregnated with wet resin and theentire second subassembly is resin cured to rigidify the same and resinbond internally, as well as to the secondary covering layer 126 and thethickened outer facing layer 128 which have been previously cured. Theresulting assembly may than be removed from the mold 118 and will appearas shown in FIG. 9.

In the foregoing boat hull assembly and in any other assembly where itmight be advantageous, usual procedures of vacuum forming may be used asdesired. Furthermore, vacuum or pressure may be used to force wet resininto internal portions of the fabric layers and the lines of stitchingthereof where advantageous and by usual well known procedures.

Another example of use of a basic core structure formed by the methodsof the present invention for forming an overall final assembly isillustrated in FIG. 14, wherein the basic core structure of FIG. 7 andpreviously described is integrated into a panel assembly with asecondary covering layer 132 and rigid outer facing layers 134. Thebasic core structure is formed as before, the primary base and coveringlayers 104 and 106, as well as the lines of stitching 108, are coveredand impregnated with wet resin, the secondary covering layer 132 appliedcovered and impregnated by the wet resin, the rigid outer facing layers134, preferably of wood or composition, are applied and the entireassembly cured for rigidifying the resin. The resulting overall assemblywill be solid and strong, particularly due to the resin rigidifying ofall fabric layers and the resin bonding of all abutting fabric layerparts, while the resin will equally bond the fabric layers to the outerfacing layers 134.

Thus, according to the principles of the present'invention, methods offabricating cellular foam core structures and assemblies are providedwith the resulting structures all involving a new concept of compositefoam and resin rigidified fabric, such construction being virtually thereverse of the concepts used in the prior constructions. Furthermore,the cellular foam core structures and assemblies resulting from themethods of fabrication herein involved are extremely versatile, both asto the wide variety of final overall assemblies into which theymay beintegrated and the degrees of forming which may be incorporated therein.Despite this extreme versatility, the cellular foam core structures andassemblies resulting from the methods of fabrication of the presentinvention are quite simple and basic in fabrication method and may beformed from a wide choice of materials.

I claim:

1. In a method of forming a cellular foam core structure assembly, thesteps of: preforming a series of longitudinally extending foam cores ofa closed cell plastic foam material having defined transverse crosssections and with all surfaces in transverse cross section beingsubstantially flat, each core in said transverse cross section having alower base side and generally oppositely transversely facing sides; withsaid foam cores in positions side by side generally transverselyadjacent extending generally parallel in said longitudinal extension andgenerally transversely side by side aligned, covering all of said foamcore lower base sides with a primary base layer of relatively flexiblefabric extending only progressively substantially continuouslytransversely and longitudinally along said foam core lower base sideswhile maintaining said primary base layer substantially free of anyupward projection between said side by side transversely adjacent foamcores; with said foam cores in said side by side transversely adjacentpositions extending generally parallel in said longitudinal extensionand generally transversely side by side aligned, covering all of saidfoam cores with a primary covering layer of relatively flexible fabricextending only progressively from said primary base layer substantiallycontinuously upwardly over and downwardly transversely between saidtransversely adjacent foam cores to said primary base layer; with saidfoam cores in said transversely adjacent positions extending generallyparallel in said longitudinal extension and generally transversely sideby side aligned covered with said primary base and covering layers,stitching between said primary base and covering layers at transverseextremities of each of said foam cores only at said primary base layer;during said stitching, maintaining said stitching free of anyappreciable penetration of said foam cores; after said covering withsaid primary base and covering layers and said stitching, covering andimpregnating said primary base and covering layers and said stitchingthroughout with a wet resin; and curing said resin to rigidify and resinbond said primary base and covering layers and said stitching.

2. A method of forming a cellular foam core structure assembly asdefined in claim 1 in which said method includes the step of prior tosaid curing of said resin but after said covering of said foam coreswith said primary base and covering layers and after said stitching,shaping the assembly of said foam cores and fabric layers to apredetermined shape as permitted by said primary base and covering layerflexibility and curing said resin while maintaining said assembly insaid predetermined shape. 7 V

3. A method of forming a cellular foam core structure assembly asdefined in claim 1 in which said method includes the steps of prior tosaid resin curing but after said covering of said foam cores with saidprimary base and covering layers and after said stitching, applyingresin coated and impregnated secondary covering layers substantiallycontinuously covering said primary base layer at said primary base layerand substantially continuously covering said primary covering layer atleast at upper extremities of said foam cores, and curing said resin ofeach of said secondary covering layers one of before and during saidcuring of said resin of said primary base and covering layers and saidstitching to rigidity and resin bond said secondary covering layers tosaid primary base and covering layers.

4. A method of forming a cellular foam core structure assembly asdefined-in claim 1 in which said method includes the step of prior tosaid curing of said resin but after said covering of said foam coreswith said primary base and covering layers and after said stitching,shaping the assembly of said'foam cores and said primary fabric layersinto a predetermined shape as permitted by said primary base andcovering layer flexibility and carrying out said curing whilemaintaining said assembly in said predetermined shape; and in which saidmethod includes the steps of also prior to said curing of said resin ofsaid primary base and covering layer and stitching asv shape betweensubstantially continuously extending secondary covering layers of resincoated'and impregnated fabric, and one of before and during saidassembly resin curing, curing said resin of said secondary coveringlayers to rigidify and resin bond said secondary covering layers withsaid assembly in said predetermined shape.

5. A method of forming a cellular foam core structure assembly asdefined in claim 1 in which said method includes the step of prior tosaid resin curing but after the assembly of said foam cores and saidfabric layers and said stitching, shaping said assembly as permitted bysaid fabric layer flexibility to bring transversely facing of said foamcore sides into substantial abutment by virtue of shaping said assemblyto cause transverse abutment between parts of said primary coveringlayer over said foam core sides; and in which said method includes thesteps of also prior to said resin curing of said shaped assembly,sandwiching said shaped assembly between substantially continuouslyextending secondary covering layers of resin coated and impregnatedfabric, and curing said resin of each of said secondary covering layersone of before and during said curing of said resin of said shapedassembly to rigidify and resin bond said secondary covering layers withsaid shaped assembly fabric layers;

6. A method of forming a cellular foam core structure assembly asdefined in claim 1 in which said method includes the steps of prior tosaid resin curing but after the assembly of said foam cores and saidfabric layers and said stitching, applying said assembly to a rigidpreformed face layer and conforming said assembly to the shape of saidface layer, and thencuring said resin of said assembly to resin bondsaid assembly to said face layer. 7

' 7. In a method of forming a cellular foam core structure assembly, thesteps of: preforminga series of longitudinally extending foam cores of aclosed cell plastic foam'material having defined transverse crosssections and with all surfaces in transverse cross section beingsubstantially flat, each core in said transverse cross section having alower base side and generally oppositely transversely facing sides; withsaid foam cores in positions side by side generally transverselyadjacent extending generally parallel in said longitudinal extension andgenerally transversely side by side aligned, covering all of said foamcore lower base sides with a primary base layer of relatively flexiblefabric extending only progressively substantially continuouslytransversely and longitudinally along said foam core lower base sideswhile maintaining said primary base layer substantially free of anyupward projection between said side by side transversely adjacent foamcores; with said foam cores in said side by side transversely adjacentpositions extending generally parallel in said longitudinal extensionand generally transversely side by side aligned, covering all of saidfoam cores with a primary covering layer of relatively flexible fabricextending only progressively from said primary base layer substantiallycontinuously upwardly over and downwardly transversely between saidtransversely adjacent foam cores to said primary base layer; with saidfoam cores in said transversely adjacent positions extending generallyparal- .lel in said longitudinal extension and generally transverselywet resin face coat extending substantially continuously over said wetresin face coat and shaped to said face coat shape; wet resin coveringand impregnating said secondary covering layer throughout said secondarycovering layer; curing said resin of said face coat and said secondarycoveringlayer to rigidify and resin bond said face coat and saidsecondary covering layer both in said face coat predetermined shape;after said covering of said foam cores with said primary base andcovering layers and said stitching, covering and impregnating theassembly of said primary base and covering layers and said stitchingthroughout with a wet resin; applying and shape conforming said wetresin covered and impregnated assembly of saidfoam cores and saidprimary base and covering layers and said stitching to said curedresin-rigidificd face coat and secondary covering layer; applying andshaping a secondary covering layer of relatively flexible fabric to andextending substantially continuously over said foam core and primarylayer and stitching assembly at an exposed side of said assemblyopposite said resin cured rigidified face coat and secondary coveringlayer; covering and impregnating the last applied and shaped of saidsecondary covering layers with a wet resin; and curing all of theremaining of said wet resin to rigidify and resin bond the remainder ofthe overall assembly to said previously cured resin rigiditied face coatand secondary covering layer.

8. A method of fonning a cellular foam core structure assembly asdefined in claim 7 in which said wet forming and shaping of saidthickened face coat includes the wet forming and shaping of saidthickened face coat at least partially curved in a direction at leasttransversely of said foam cores in said overall assembly.

9. A method of forming a cellular foam core structure assembly asdefined in claim 7 in which said wet forming and shaping of saidthickened face coat includes the wet forming and shaping of saidthickened face coat at least partially curved both transversely andlongitudinally of said foam cores in said overall assembly.

10. A method of forming a cellular foam core structure assembly asdefined in claim 7 in which said wet forming and shaping of saidthickened face coat includes the wet forming and shaping of saidthickened face coat into a shape that said foam cores in said conformedand shaped overall assembly have transversely facing sides one to thenext substantially transversely abutting by virtue of transverseabutment and resin bonding between parts of said primary covering layerover said foam core transversely facing sides, and wet forming andshaping said thickened face coat at least partially curved 7

1. In a method of forming a cellular foam core structure assembly, thesteps of: preforming a series of longitudinally extending foam cores ofa closed cell plastic foam material having defined transverse crosssections and with all surfaces in transverse cross section beingsubstantially flat, each core in said transverse cross section having alower base side and generally oppositely transversely facing sides; withsaid foam cores in positions side by side generally transverselyadjacent extending generally parallel in said longitudinal extension andgenerally transversely side by side aligned, covering all of said foamcore lower base sides with a primary base layer of relatively flexiblefabric extending only progressively substantially continuouslytransversely and longitudinally along said foam core lower base sideswhile maintaining said primary base layer substantially free of anyupward projection between said side by side transversely adjacent foamcores; with said foam cores in said side by side transversely adjacentpositions extending generally parallel in said longitudinal extensionand generally transversely side by side aligned, covering all of saidfoam cores with a primary covering layer of relatively flexible fabricextending only progressively from said primary base layer substantiallycontinuously upwardly over and downwardly transversely between saidtransversely adjacent foam cores to said primary base layer; with saidfoam cores in said transversely adjacent positions extending generallyparallel in said longitudinal extension and generally transversely sideby side aligned covered with said primary base and covering layers,stitching between said primary base and covering layers at transverseextremities of each of said foam cores only at said primary base layer;during said stitching, maintaining said stitching free of anyappreciable penetration of said foam cores; after said covering withsaid primary base and covering layers and said stitching, covering andimpregnating said primary base and covering layers and said stitchingthroughout with a wet resin; and curing said resin to rigidify and resinbond said primary base and covering layers and said stitching.
 2. Amethod of forming a cellular foam core structure assembly as defined inclaim 1 in which said method includes the step of prior to said curingof said resin but after said covering of said foam cores with saidprimary base and covering layers and after said stitching, shaping theassembly of said foam cores and fabric layers to a predetermined shapeas permitted by said primary base and covering layer flexibility andcuring said resin while maintaining said assembly in said predeterminedshape.
 3. A method of forming a cellular foam core structure assembly asdefined in claim 1 in which said method includes the steps of prior tosaid resin curing but after said covering of said foam cores with saidprimary base and covering layers and after said stitching, applyingresin coated and impregnated secondary covering layers substantiallycontinuously covering said primary base layer at said primary base layerand substantially continuously covering said primary covering layer atleast at upper extremities of said foam cores, and curing said resin ofeach of said secondary covering layers one of before and during saidcuring of said resin of said primary base and covering layers and saidstitching to rigidity and resin bond said secondary covering layers tosaid primary base and covering layers.
 4. A method of forming a cellularfoam core structure assembly as defined in claim 1 in which said methodincludes the step of prior to said curing of said resin but after saidcovering of said foam cores with said primary base and coveriNg layersand after said stitching, shaping the assembly of said foam cores andsaid primary fabric layers into a predetermined shape as permitted bysaid primary base and covering layer flexibility and carrying out saidcuring while maintaining said assembly in said predetermined shape; andin which said method includes the steps of also prior to said curing ofsaid resin of said primary base and covering layer and stitchingassembly, sandwiching said assembly in said predetermined shape betweensubstantially continuously extending secondary covering layers of resincoated and impregnated fabric, and one of before and during saidassembly resin curing, curing said resin of said secondary coveringlayers to rigidify and resin bond said secondary covering layers withsaid assembly in said predetermined shape.
 5. A method of forming acellular foam core structure assembly as defined in claim 1 in whichsaid method includes the step of prior to said resin curing but afterthe assembly of said foam cores and said fabric layers and saidstitching, shaping said assembly as permitted by said fabric layerflexibility to bring transversely facing of said foam core sides intosubstantial abutment by virtue of shaping said assembly to causetransverse abutment between parts of said primary covering layer oversaid foam core sides; and in which said method includes the steps ofalso prior to said resin curing of said shaped assembly, sandwichingsaid shaped assembly between substantially continuously extendingsecondary covering layers of resin coated and impregnated fabric, andcuring said resin of each of said secondary covering layers one ofbefore and during said curing of said resin of said shaped assembly torigidify and resin bond said secondary covering layers with said shapedassembly fabric layers.
 6. A method of forming a cellular foam corestructure assembly as defined in claim 1 in which said method includesthe steps of prior to said resin curing but after the assembly of saidfoam cores and said fabric layers and said stitching, applying saidassembly to a rigid preformed face layer and conforming said assembly tothe shape of said face layer, and then curing said resin of saidassembly to resin bond said assembly to said face layer.
 7. In a methodof forming a cellular foam core structure assembly, the steps of:preforming a series of longitudinally extending foam cores of a closedcell plastic foam material having defined transverse cross sections andwith all surfaces in transverse cross section being substantially flat,each core in said transverse cross section having a lower base side andgenerally oppositely transversely facing sides; with said foam cores inpositions side by side generally transversely adjacent extendinggenerally parallel in said longitudinal extension and generallytransversely side by side aligned, covering all of said foam core lowerbase sides with a primary base layer of relatively flexible fabricextending only progressively substantially continuously transversely andlongitudinally along said foam core lower base sides while maintainingsaid primary base layer substantially free of any upward projectionbetween said side by side transversely adjacent foam cores; with saidfoam cores in said side by side transversely adjacent positionsextending generally parallel in said longitudinal extension andgenerally transversely side by side aligned, covering all of said foamcores with a primary covering layer of relatively flexible fabricextending only progressively from said primary base layer substantiallycontinuously upwardly over and downwardly transversely between saidtransversely adjacent foam cores to said primary base layer; with saidfoam cores in said transversely adjacent positions extending generallyparallel in said longitudinal extension and generally transversely sideby side aligned covered with said primary base and covering layers,stitching between said primary base and covering layers at transverseextremities of eAch of said foam cores only at said primary base layer;during said stitching, maintaining said stitching free of anyappreciable penetration of said foam cores; wet forming and shaping athickened face coat including a wet resin and having a predeterminedshape; applying a secondary covering layer of relatively flexible fabricto said wet resin face coat extending substantially continuously oversaid wet resin face coat and shaped to said face coat shape; wet resincovering and impregnating said secondary covering layer throughout saidsecondary covering layer; curing said resin of said face coat and saidsecondary covering layer to rigidify and resin bond said face coat andsaid secondary covering layer both in said face coat predeterminedshape; after said covering of said foam cores with said primary base andcovering layers and said stitching, covering and impregnating theassembly of said primary base and covering layers and said stitchingthroughout with a wet resin; applying and shape conforming said wetresin covered and impregnated assembly of said foam cores and saidprimary base and covering layers and said stitching to said cured resinrigidified face coat and secondary covering layer; applying and shapinga secondary covering layer of relatively flexible fabric to andextending substantially continuously over said foam core and primarylayer and stitching assembly at an exposed side of said assemblyopposite said resin cured rigidified face coat and secondary coveringlayer; covering and impregnating the last applied and shaped of saidsecondary covering layers with a wet resin; and curing all of theremaining of said wet resin to rigidify and resin bond the remainder ofthe overall assembly to said previously cured resin rigidified face coatand secondary covering layer.
 8. A method of forming a cellular foamcore structure assembly as defined in claim 7 in which said wet formingand shaping of said thickened face coat includes the wet forming andshaping of said thickened face coat at least partially curved in adirection at least transversely of said foam cores in said overallassembly.
 9. A method of forming a cellular foam core structure assemblyas defined in claim 7 in which said wet forming and shaping of saidthickened face coat includes the wet forming and shaping of saidthickened face coat at least partially curved both transversely andlongitudinally of said foam cores in said overall assembly.
 10. A methodof forming a cellular foam core structure assembly as defined in claim 7in which said wet forming and shaping of said thickened face coatincludes the wet forming and shaping of said thickened face coat into ashape that said foam cores in said conformed and shaped overall assemblyhave transversely facing sides one to the next substantiallytransversely abutting by virtue of transverse abutment and resin bondingbetween parts of said primary covering layer over said foam coretransversely facing sides, and wet forming and shaping said thickenedface coat at least partially curved both transversely and longitudinallyof said foam cores in said overall assembly.